Coolant flow problem

Driving to work one morning and it was very cold like around 15. (Cold for Albuquerque) Truck heater never got hot on the way to work. Once I arrived at work I noticed a coolant leak coming from the water pump. Also, noticed the upper hose on the radiator was very hot and the lower hose was cold. Like real cold. Two things I thought it could be; Water pump because of the leak or the thermostat do to the cold bottom radiator hose.
I changed out the thermostat and no change. (Boiled the thermostat and it opened at 190). Then I change out the water pump and again no change.

Ok now I'm thinking that something is blocking the flow. Disconnected the radiator hoses and flowed water through the top hose and watch it come out the bottom hose. Flowed water through the top (radiator cap) and water flowed through the bottom. Next I flowed water thought the inlet of the motor and water come out the other side. Then I disconnected the heater hose to the heater coil and water flowed through there.
What did I miss???? Any ideals what it could be?
Thanks for the help.
Ralph